Growing Up
by UranoMetriaPrincess
Summary: Fionna drops the news that she will be leaving Aaa, to go on an adventure of her own. She wants to become stronger to protect the people she loves and to grow up into the woman she's destined to be. How will everybody take the news? What will happen when she returns? Will the boy she loves return her affections once home? Find out! FIOLEE! Rated M for language and sexual themes.


**GROWING UP**

**CHAPTER ONE: DRAMA BOMB**

**Hey everybody! Hope you all enjoy!**

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The blonde adventuress at the ripe age of sixteen, walked through the front door of the tree fort she called her home. She just came back from helping Hot Dog Prince, get rid of a wolf that had been stalking him and his tiny- size not numbers, army. Thankfully no one had gotten hurt by the time she showed and the wolf was easy to take care of. To sum it up, it was a boring adventure- if one would even it that. The whole time she was lost in her thoughts- not sparing much attention to the wolf.

Fionna, was lost in her thoughts a lot recently. Thinking about her future. She loved the life she had built in Aaa, but something was missing. Now that she was sixteen, she was much more skilled than she had been when she first became the heroine famed across land of Aaa and beyond. Her life had simply become a little boring. She wanted to protect Aaa, and all of her friends and family that lived in it's land- that had not changed. What changed was her desire to stop fighting such miniscule things. She wanted to be able to fight anything that came her way. On her own.

Speaking of _on her own_, that simply meant, Cake. Her feline sister she loved with all of her heart. She knew she relied on her magical stretching abilities in tough fights- and she didn't want that. That's not to say she wants to stop going on adventures with her sister, she would forever if she could. But Cake had a life of her own.

Fionna, could see the longing on Cake's face when they ran across families that lived together happily with hoards of children. Fionna, also knew she was the reason why Cake didn't chase after that dream. She was scared to leave the young adventuress on her own. Fionna had tried to sit her down and tell her she was fine, but Cake started crying about how she's never been on her own before and doesn't want her to think she was abandoning her. The conversation ended there, both sisters in tears and hugging each other. Fionna wanted to continue, but she held her tongue and planned to pick it back up on a later date.

She planned to pick that conversation back up today. As much as she would love spending the rest of her days at the side of her sister, she wanted Cake happy. She would be happy to spend the rest of her life at Cakes side from a distance. Fionna, also wanted a chance to grow.

She wanted to learn how to be independent, to get stronger, travel places she's never been, learn new things, and find love. She simply wanted an adventure.

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"Cake! You here?" Fionna called as she climbed up the later leading to the main floor.

"I'm in the kitchen making tea, Baby!" the feline answered.

Fionna finished climbing up the later and headed to the couch- ungracefully plopping herself down after dropping her bag on the floor. "I'd like to talk to you after you're done, Cake."

Cake glanced over her shoulder with a skeptical look at the serious tone her sister used. Cake finished steeping her tea and walked over to Fionna, sitting down herself, "What's on your mind, Baby Cakes?"

Fionna sat silent for a minute staring at the floor, composing her thoughts. With a sigh, Fionna began to speak, "Do you ever want more out of life, Cake?" She finally lifted her head to look at Cake- her face held a longing gaze.

Cake didn't know where this conversation was going yet, but she knew she wasn't going to like the outcome very much. "What do you mean, Fionna?" Cake asked.

"What I mean is, don't you want to begin a life of your own? To start a new adventure? Finally settle down with Lord M? Have children?" Fionna held a knowing gaze. She knew Cake wanted these things, they just needed to sit down and talk about arrangements- which is what they were going to do today she decided.

Cake raised her eyebrow, now suspicious of what her sister was talking about, "Baby, if this is about me moving out, we al-"

Cake was cut off by her sister, "That is what I want to talk about; no, need to talk about. I want you to be happy, Cake. I want you to stop putting your life on hold for me. I'm growing up, Cake. I think it's time we both start a new adventure in our life." Fionna had a small warm smile on her face while Cake sat next to her with watery eyes.

Finally, Cake saw reason, "I know we do, Fionna. I was just worried about you and our relationship I guess. I don't want you to think I'm cutting you out of my life. Lord, actually asked me to marry him awhile ago, I told him that I needed to sort things out first. I guess that's where we are now. I love you Girl, and I'm glad you sat me down to talk about this. You mean so much to me." Cake pulled her sister into a bone crushing hug.

Fionna smiled at the love she felt, "I'm glad too, Cake. I can't wait to have a brother-in-law and lots of nieces and nephews. I think you guys should move into the tree house after you guys get married. There's more room here and it's a great place for kids to grow up."

"But Fionna, Honey, where would you live?" Cake pulled away from the hug and gave Fionna a questioning look. Fionna suddenly looked nervous and Cake didn't like that.

With a small nervous laugh, Fionna spoke, "Haha, about that… You see, I knew this was coming and I was thinking about what I wanted to do with my future. I want an adventure of my own. I want to travel, and learn, and find the important things in life. I want to leave Aaa, and get stronger. I don't think I'd be gone too long, a year at most."

Cake was shell-shocked to say the least. It took a minute to snap out of her spiralling thoughts, "A YEAR! WHAT DO YOU MEAN LEAVE, AAA? I TELL YOU I'M GETTING MARRIED AND YOU WANT TO LEAVE?" Cake was panting after yelling.

Fionna looked sheepish, she knew this would happen, "Cake, settle down. I know it's a lot to take in, but you need to breathe. I was planning on leaving after you guys got married, I wouldn't miss that for the world, Cake. You know I love you, I just need to do this for myself."

Cake sighed, she knew she wasn't going to change the young adventuress' mind. She had obviously been thinking about this for quite some time and the girl was as hard-headed as they came. "Okay, Okay. I know I'm not going to change your mind on this. I support you, but it doesn't mean I have to like it. I'm going to miss you so much, Fionna." Cake smiled at her stubborn sister.

"Thank you, Cake. Thank you for always having my back. Do you think you could call PG and tell him to gather our friends tonight so we can announce our news? Don't tell him what's going on. I'm going to take a bath now, I got dirty today," with that, Fionna climbed up to their bedroom's attached bathroom and started her bath.

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_**LATER THAT NIGHT**_

Prince Gumball cleared his throat standing on a pedestal at the front of the room, gathering everyone's attention "Okay everyone! Thank you all for coming on such short notice! Fionna and Cake would like to share some news with us, so without further edu, here they are!" The pink prince smiled at the sisters as they walked up the pedestal.

Cake was standing with Lord Monochromicorn at her side looking a mix of happy and sad while Fionna was blushing at the eyes of the whole room on them. Finally, Cake spoke up, "Hello Everyone, thank you again for coming. I'll share my news with you all first," she paused and smiled up at her fiance, "We're getting married!"

The whole room, as expected started cheering. Lumpy Space Prince was yelling "DRAMA BOMB!" while getting on his phone to blog about the news of the soon to be marriage, PG's mind was swirling with thoughts of planning the wedding with hearts in his eyes, BMO had hearts displayed on his screen, even Marshall Lee had a smile on his face.

Lord Monochromicorn tapped his foot on the ground multiple times, probably thanking everyone for their support but with the exception of a few, a guess was the best they had. When the cheering and congratulatories were settled down, Fionna stepped up.

She cleared her throat before speaking, "Hi everyone. I would like to share that after my sister gets married, I'm going to be leaving for about a year. I'm going on an adventure of my own. I want to travel and get stronger. I'm very sorry I'm making you all sad with this news, but I need to do this for myself."

She smiled warmly at the people gathered in front of her. They were her family. She was doing this for them too, to be able to protect them when the time comes. She held such fond memories with each one, she knew this would be hard. But leaving a few individuals behind would be the hardest. Cake, her beloved sister. Prince Gumball, her best friend and voice of reason. Lastly, Marshall Lee. The boy who held her affections. She loved the Vampire King. He didn't know, she knew he didn't return her affection and she was okay with that for now. She knew he still saw her as a girl. But she would return a woman and he would be forced to see that. She could only hope that one day they could be together.

Fionna was thrown out of her thoughts at the yelling of LSP, "OH MY GLOB! EVEN BIGGER DRAMA BOMB!" After LSP yelled the whole room once again erupted in yelling, but of sadness and anger instead of cheers.

BMO was wailing on the ground, Gumball was openly crying and looked like someone took out his candy heart and put it through a shredder, LSP was now flying in circles with her hands up still yelling about a drama bomb, Tree Stumps was a puddle on the ground weeping, and Marshall looked angry, refusing to meet her gaze.

* * *

Their impromptu get together was finally over after tons of questions. Eventually everyone gave their blessing. Well, everyone but one. Marshall Lee had abruptly flown out not long after she announced she would be leaving. She knew he was going to be upset, she would have to walk to his house and talk to him. She sighed, tonight was exhausting and it wasn't even over. Her heart had been through an emotional ringer tonight. On her way home, she excused herself from Cake, saying she needed to talk to someone. Cake nodded and told her she'd see her later.

It was probably 11 by the time she reached the front door of Marshall Lee's house. She could hear his radio blasting rock in the house, yep, he was upset. She finally got the courage to knock on his door.

The radio shut off and a moment later his door opened. He was blocking the entrance to his house with a scowl on his face. "What?" he answered dejectedly.

She sighed, "I just want to talk with you Marshall."

He scoffed, "Shouldn't you be at home packing?"

"No. Where I need to be is right here, knowing you're okay," she looked up at him with sad eyes, she hated that she hurt the person she loves.

"HOW AM I SUPPOSED TO BE _OKAY_ WITH YOU LEAVING FOR A FUCKING YEAR, FI! YOU'RE MY BEST FRIEND! HOW AM I SUPPOSED TO BE OKAY WITH MY BEST FUCKING FRIEND LEAVING ME! THAT'S SO SELFISH OF YOU!" Marshall was in full demon mode now, eyes just slits, fangs elongated, and tongue hissing.

"WE'RE BOTH BEING SELFISH OKAY!?" Fionna suddenly yelled. She looked down, tears streaming down her face. With a small voice she continued, " I want to leave, and you need to let me leave."

The atmosphere was deafeningly quiet, both not looking at one another. Finally, Marshall sighed and stepped forward, embracing the blonde in a tight embrace. He buried himself in her neck and whispered, "I'm going to miss you."

She held onto him tighter and whispered back, "I'm going to miss you too. When I get back, I promise I'll never leave again."

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**Thank you so much for reading! This is my first Adventure Time fanfiction I'm writing. Let me know what you think! I'm excited to see where this story goes and hope you're along for the ride! But first… FIOLEE FOR THE WIN. I can't wait to get into their romance, GAHHHHHHHH.**


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